The invention is generally related to devices to shut off the flow of fluids through a fluid conduit, and more particularly to a device that floats in a fluid contained in a reservoir, and when the fluid therein reaches a certain level, the device automatically closes an orifice in such reservoir to prevent further fluid flow, while in particular preventing passage of air therethrough.
In patient care facilities, infusion of a parenteral solution into a patient may be achieved by suspending an inverted bottle or fluid reservoir above the patient and interconnecting a fluid administration set between the reservoir and the patient. The administration set may include a vented penetrant to pierce the stopper of the reservoir and a transparent drip chamber connected in series with the administration set tubing, through which the rate of parenteral solution flow can be monitored. The distal end of the tubing is connected to a cannula that is inserted into a blood vessel of the patient. A pinch valve and/or pumping mechanism engaged with the tubing may be actuated to compress the walls of the tubing, thereby restricting fluid flow therethrough to regulate the flow to a selected rate.
In therapeutic fluid administration systems, it is important that introduction of air into a patient's blood vessel be limited. Should air be introduced into a blood vessel, a condition known as air embolism may result whereby an air bubble may form in such blood vessel causing a blood flow obstruction therein. Air embolism has proven fatal in some instances. Consequently, it is desirable to include an automatic shut off device within a fluid administration set that prevents air from being introduced into tubing leading to a patient's blood vessel; the shut off device being operative once the parenteral fluid contained in the fluid container of the administration set has been exhausted.
It is well known that therapeutic fluid administration sets including drip chambers are subject to being tilted to one side as fluid administration is being conducted. This may occur, for instance, when a patient is being transported to or from a patient care facility or when the patient is being moved to different locations within the facility. In addition, attendants may inadvertently set up the administration set in a tilted position. Therefore in order to be effective, a fluid shut off device must be capable of providing a reliable air tight seal even if the fluid administration set is tilted.
Other fluid shut off devices have been provided that include floating valve members such as balls or disks that seat on an outlet port to prevent the passage of air therethrough. It has been noted in some fluid shut off devices that include a floating ball that the ball may begin spinning and/or bobbing in the fluid at high fluid flow rates. The spinning of the ball caused by high flow rates appears to result in the ball bobbing in the fluid. Should the bobbing ball approach the valve seat too closely, it may actually seat prematurely and stop flow before emptying the fluid reservoir. An attendant would then need to dislodge the ball to resume flow. This may result in lost time that the patient could have received the medication from the reservoir.
A consideration pertinent to floating flow stop devices is that they must reliably shut off flow. The floating member must not be subject to binding or sticking in an open position and must be guided to properly engage the valve seat. Some manufacturers have taken the approach of providing a cage-like component that confines a floating disk to a limited range of movement over the outlet port to avoid sticking and improper seating. However, the inclusion of such a confinement cage increases the costs of manufacture of such a shut off valve making it less desirable.
A further consideration in the design of floating shut off valves is the ability to dislodge the seated floating member from the valve seat when needed to resume infusion. Ease of dislodging is desirable so that time is not wasted in attempting to pry the floating member off the seat. Preferably, the floating member should be dislodgable by a simple action of the attendant.
Another flow shut off device includes a floating disk disposed in a fluid chamber where the chamber has outer side walls shaped to provide alignment surfaces to the disk to properly align the disk into sealing contact with a valve seat. This approach requires a specially formed outer wall for the chamber making the retrofit or adaptation of existing straight walled chambers difficult. Additionally, shaped outer walls many times have the effect of strengthening the wall thereby making it more difficult to dislodge the sealing device from the valve seat by squeezing the walls together. Shut off devices having float containment cages may also interfere with the operator's attempts to dislodge the float member.
It is also desirable that the administration set including the fluid shut off device be made available as inexpensively as possible because such fluid administration sets are discarded after use.
Hence, those skilled in the art have recognized the need for a disposable administration set including a reliable fluid flow shut off device that provides an effective seal to prevent the passage of air. The shut off device should also be easily releasible when it is desired to resume flow. In addition, a device of this nature should be cost effective and easy to manufacture. The present invention meets these needs and others.